<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Test02</title>
</head>
<body>
<script type="text/javascript">
    let obj = {
        "a": 10,
        "b": 20
    };

    // delete obj["a"];
    Reflect.deleteProperty(obj, "a");

    console.dir(obj);
    // console.log("a" in obj);
    console.log(Reflect.has(obj, "a"));
    console.log(Reflect.has(obj, "b"));
</script>
</body>
</html>